March 31, 2009

Study: Size matters in snail shells

U.S. biologists have finished a study started in 1915, determining snail shells can significantly increase in size during a relatively short period of time.

The University of Pennsylvania researchers focused on the snail Nucella lapillus and found the snail experienced a dramatic increase in the size of its shell during less than a century, providing a clear illustration of how fast and effectively change can occur.

The biologists said their most striking finding, which was not previously reported, is that the shell of Nucella lapillus, the Atlantic dogwhelk, increased at all 19 sites where samples were taken. Shell lengths increased by an average of 22.6 percent during the past century, with no evidence of changes in other shell characteristics.

The Penn team said its comparisons were based on archived shells collected from 1915 to 1922 from sites that were resampled during 2007.

This increase in size is a stunning observation, especially since dogwhelks are one of the best known and most widely studied organisms in the North Atlantic Ocean, said Professor Peter Petraitis. Imagine that much change in the height of humans occurring between 1915 and 2007. In 1915, the height of the average Ivy League man was 5 feet 9 inches. A 23 percent increase would now make the average height slightly over 7 feet.

The study appears in the Proceedings of the National Academy of Sciences.